Optimized cooling: less cooling oil for low system pressures, more cooling oil for high system pressures
Automatic idle shift system at vehicle standstill and engaged service break (stand-by control)
One transmission – many possibilities
For the 8-speed automatic transmission, ZF set out to design and develop an entirely new gear set concept. The result is a revolution in transmission design: a transmission concept with 4 gearsets which requires only 5 shift elements – of which only two are open in any given gear. The 8HP also requires no more than 3 multi-disk clutches and 2 brakes, which allows it to achieve a greater degree of efficiency than other concepts. As a result of the fact that only 2 shift elements are open per gear, drag losses in the transmission are sustainably reduced. This effect is supported by the use of a new parallel-axis vane-type oil pump. 4 A torque range from 300 to 1000 newton meter makes the 8HP the perfect partner for all rear-wheel-drive and all-wheel-drive designs. From the lower midsize segment to sporty luxury cars, and in every type of SUV and offroad vehicle – its revolutionary design is always an efficient and economical solution. Although the 8HP features 2 more speeds than the extremely successful 6HP, the dimensions have remained unchanged and the weight was even reduced by 3% to 87 kg (transmission modular system 8HP70) including oil. At the same time, the total transmission ratio spread of 7.0 ensures that the engine is always in its optimum operating range. This translates into improved acceleration and reduced fuel consumption.
Based on a really successful product, it combines dynamics and comfort with improved efficiency – also with regard to the costs. And it is ideally equipped for even stricter fuel consumption and CO2 emission regulations. In the premium and mid-size car range, the optimized 8HP product family enables the average fuel consumption to be cut by another 3%. CO2 emissions decrease to the same extent. These potentials can also be completely transferred to hybrid drives. Incidentally, additional savings potential by a further optimized startstop function is not yet included here. To achieve these innovations, ZF engineers have optimized some details. Thus, the reduction of drag torques and engine speeds further reduced the already very low power losses. Essential success aspects are the higher transmission ratio spread and the reduction of system pressures in many areas. Another factor is the multidisk separation of the brakes. Furthermore, advanced torsional vibration dampers enable a faster bypassing of the hydrodynamic power transmission and therefore further reduction in speed. Thus, the new 8HP is perfectly prepared for use with the new engines (3-8 cylinders) which will determine the trend of the years-to-come.